1. Field of the Invention
This invention relates to the field of spatially stabilizing projected or viewed images which are projected or created from a film or other image bearing source onto a projection screen or suitable location wherein the image appearing thereat is subject to movement such as weaving or jitter resulting from imperfections in the projection system or image bearing source. The invention finds particular use for stabilizing projected optical images from film and television projectors, graphics printers or images photographed by a camera such as a still video or television camera.
In the presentation, viewing or capture of images, problems often occur which cause movement, jitter and/or distortion of the image. Electro mechanical and optical mechanical devices such as projectors and cameras are highly susceptible to such problems.
One of the most common of mechanical effects occurs with film projectors and is called gate weave in the motion picture industry. Gate weave results in a moving and jittery image being presented on the motion picture screen when the movie is projected due to slight movement of the projected film image. The main cause of gate weave in this instance is the improper positioning of the film image in the film gate or aperture of the projector from one frame to the next due to uneven wearing of the sprocket holes in the film occurring over prolonged use. The sprocket holes are used by the projector intermittent gear to position the film in the projector aperture for the momentary presentation of each frame, with the edges of the holes requiring critical alignment with respect to the film image. As the film is projected over and over, these edges tend to wear unevenly.
The parent application of this specification deals with an invention which can effectively correct the above problems. The present specification deals with an improvement to the previous invention which utilizes specific features of the image bearing medium in order to provide lower cost and/or higher performance corrections. In particular, the preferred embodiment of the invention finds considerable use with motion picture film which includes digital audio tracks.
2. Description of the Prior Art
In the Prior art it is known to apply considerable mechanical precision to the movement and holding of the image bearing or image receiving element of imaging systems. In particular film projectors having elaborately designed film movement and positioning mechanics are well known. In the field of acquiring images, such as in film and television cameras, elaborate types of vibration and movement damping mechanisms are used, these including electromechanical gyroscope mechanisms to hold the camera or its mounting platform steady.
It is also known in the television industry to electronically correct a jittering television image by the electronic process of moving the video image signal with respect to its horizontal and vertical synchronizing pulses with the aid of complex motion detection circuits and frame memory control. Such systems do not lend themselves to improvement of existing projection and camera equipment and in particular to the improvement of existing motion picture film and television projectors.